The present invention relates to aromatic 4,6-bis(trichloromethyl)-s-triazin-2-yl compounds, a process for their preparation and their use as photoinitiators in light-sensitive mixtures. The compounds according to the invention are also useful intermediates for the preparation of highly-active photoinitiators or photolytically-active acid donors for light-sensitive mixtures.
4,6-Bis(trichloromethyl)-s-triazin-2-ylphenyl compounds are known in many forms; a detailed description of various compounds of this type is provided by M. Wakabayashi et al., Bull. Chem. Soc. Jpn., 42, 2924 (1969). The phenyl ring in these compounds can be substituted by relatively inert chemical groupings, such as, for example, nitro, alkyl or alkoxy groups or halogen atoms.
WO 81/02262 discloses light-sensitive mixtures containing 4,6-bis(trichloromethyl)-s-triazin-2-ylphenyl derivatives as photoinitiators in which the aromatic ring is substituted by 1 to 3 alkyl or alkoxy groups. The light-sensitive mixtures described are used for the preparation of pressure-sensitive adhesive tape. The photoactivity of these compounds is in the near UV region.
The above-mentioned 4,6-bis(trichloromethyl)-s-triazin-2-ylphenyl derivatives are not important in practice as intermediates, since they cannot be further reacted or can only be further reacted with at least partial destruction of the trichloromethyl groups.
On the other hand, it is known that certain 4,6-bis(trichloromethyl)-s-triazin-2-yl derivatives have very good properties as photoinitiators and photolytic acid donors. Examples of this type of compound are known from DE-C 2,718,259, in which substituted or unsubstituted 4,6-bis(trichloromethyl)-s-triazin-2-ylnaphthyl derivatives are described, or from EP-A 0,137,452 from which substituted or unsubstituted 4,6-bis(trichloromethyl)-s-triazin-2-ylstyrylphenyl derivatives which can be used as photoinitiators originate. Although the compounds mentioned in this publication are highly active in the near UV region and to some extent also in the visible region, they have the disadvantage that their preparation is frequently very complicated, expensive and time-consuming.
There is therefore a demand for novel 4,6-bis(trichloromethyl)-s-triazin-2-yl derivatives that can be converted with comparative synthetic ease while maintaining the trichloromethyl groups intact into chromophore-substituted compounds having high photoactivity as initiators in photopolymerizable mixtures or as acid donors in mixtures which can be cleaved by acid in the near UV region or in the visible region.